Air springs are in common use for motor vehicles and various machines and other equipment. The springs are designed to support a suspension load such as a vehicle. The springs are often combined with a separate shock absorber device in the suspension that functions to dampen oscillations. Air springs typically consist of a flexible elastomeric reinforced sleeve that extends between a pair of end members. The sleeve is attached to end members to form a pressurized chamber therein. The end members mount the air spring on spaced components or parts of the vehicle or equipment on which the air spring is to be mounted.
The internal pressurized gas, usually air, absorbs most of the motion impressed upon or experienced by one of the spaced end members by which the air spring is mounted. The end members move inward toward each other and also away as the motion of the suspension requires.
It is desired in certain applications to provide an air spring for an automotive suspension system designed to operate at two or more suspension ride heights. Such a spring typically will have a fabric reinforced rubber sleeve that forms a rolling lobe that rolls on a piston(s) at either one or both ends of the spring. The piston(s) can either be cylindrical or have conical tapers that will either increase the spring rate with a positive taper or decrease the spring rate with a negative taper. A multiple ride height air spring will have the lobe rolling over different portions of the piston(s) at each height, and these different piston portions can have specific conical tapers to influence the spring rate at that ride height.
With a multi-ride height suspension, it is often desirable, such as in off-road SUV vehicles, to have a higher suspension spring rate at the taller or higher suspension ride height(s) to improve vehicle stability, safety, and ride comfort, when driving over uneven surfaces. In order to move the air spring from a shorter height to a taller height, it is typical to add a large amount of internal air volume to the air spring. This additional internal air volume, however, greatly reduces the spring rate of the air spring well beyond the capability of design tools such as piston tapering or other air spring shaping to correct. The reduction in air spring rate attendant the taller height mode of operation thus n's counter to the desired objective of a higher spring rate at higher heights in order to achieve the aforementioned off-road performance objectives.
The industry, accordingly, is in need for a multi-height air spring that includes means for efficiently, predictably, and reliably functioning at multiple heights. The desired air spring, moreover, must function at multiple heights and provide means for creating a higher spring rate at the higher heights and a lower spring rate at the lower heights. The optimum air spring ideally should achieve these objectives in a design that is cost-effective to manufacture, assembly, deploy, and maintain.